Highly castable, weldable, oxidation resistant alloys

ABSTRACT

Special highly castable and weldable heat resistant alloys containing nickel, manganese, silicon, chromium, carbon, iron, boron and molybdenum afford high temperature oxidation resistance and characteristics which render the alloys particularly suitable for the casting of thin section components for use at elevated temperatures under oxidizing conditions.

" United States Patent Forbes Jones et a].

[4 1 July 1, 1975 HIGHLY CASTABLE, WELDABLE,

OXIDATION RESISTANT ALLOYS Inventors: Robin Mackay Forbes Jones,

Suffern, N.Y.; Walter Adrian Petersen, Ridgewood, NJ.

- Assignee: The International Nickel Co., Inc.,

New York, NY.

Filed: Dec. 13, 1974 Appl. No.: 532,330

Related U.S. Application Data Continuation-impart of Ser. No. 384,799,Aug. 2, 1973, abandoned.

U.S. Cl. 29/l96.1; 75/122; 75/128 A; 75/128 C; 75/128 F; 75/128 W;

Int. CL? B23? 3/00; C22C 19/05; C22C 38/44; C22C 38/54 Field of Search75/134 F, 122, 171, 128 A, 75/128 C, 128 R128 W; 29/l96.1

[56] References Cited UNITED STATES PATENTS 2,938,786 5/1960 Johnson75/171 3,758,296 9/1973 Johnson 75/122 Primary Examiner-L. DewayneRutledge Assistant ExaminerArthur J. Steiner Attorney, Agent, orFirmEwan C. MacQueen; Raymond J. Kenny [5 7 ABSTRACT 11 Claims, NoDrawings HIGHLY CASTABLE, WELDABLE, OXIDATION RESISTANT ALLOYS Thepresent invention is a continuation-in-part of application Ser. No.384,799 filed Aug. 2, 1973, now abandoned, and relates to heat-resistantalloys having excellent castability and weldability and high temperatureoxidation resistance.

It is well known that many industrial processes and applications requireheat resistant components of intricate design. To produce suchcomponents, the alloy should be highly castable; however, to becommercially useful in respect of any number of applications, the alloymust also be capable of offering good weldability characteristics topermit, for example, fabrication of the components into larger, morecomplex units and, more importantly, for the joining of the componentsto other parts of an assembly.

One application requiring alloys having both high castability andweldability is static components in vehicular turbines, e.g., shroudsand the dome and plenum chambers. These components are commonlymanufactured by special casting techniques and/or sheet fabrication,extremely expensive procedures adding greatly to cost. In thisconnection and desirably, such components should be capable of beingcast in conventional sand molds, and, in particular, in thin sectionsand molds. And, more importantly, the component should be weldablesince this allows the component to be assembled to the other parts ofthe vehicular turbine. Additionally, welding also allows for thefabrication of several small components into one large unit and forrepairing of casting defects or even service damage.

But bringing these two properties, castability and weldability, togetherin one heat-resistant alloy, particularly of the nickel-base type, isbeset with difficulty since one property is often achieved at theexpense of the other. To explain, weldable heat resistant alloys and, inparticular, heat-resistant nickel alloys containing high amounts ofchromium, are known to have relatively poor casting properties, formingfolds, cold shuts and misruns, especially when cast into thin sections.Attempts to improve casting properties have invariably led to a decreasein weldability. However, improved castability properties have beenrecently achieved through the judicious use of both silicon and boron inat least nickel-containing stainless steels. However, weldability wassuch that brazing was recommended. Now, as is well known in the art,silicon and boron are considered to be among the most detrimentalperformers in terms of weldability considerations with regard to highnickel, chromium-containing alloys. Notwithstanding this and as will bedemonstrated herein, these constituents, we have found, can be used totheir advantage but while simultaneously achieving outstandingweldability.

We have now discovered a new alloy providing a new combination ofcharacteristics, especially excellent castability and weldability,notwithstanding the pres ence of relatively high amounts of the normallyweldcracking promoters, silicon and boron, and this has beenaccomplished while obtaining good oxidation resistance and otherproperties at high temperature.

It is an object of the invention to provide an alloy having acombination of characteristics including excellent castability andweldability and resistance to oxidation at high temperatures.

Another object of the invention is to provide oxidation-resistant castalloy products and articles, including products and articles for use asstatic components in vehicular turbines.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking, the present invention is directed to an alloycontaining (by weight) up to about 1.4 percent carbon, up to about 8.5percent molybdenum, the carbon and molybdenum being specially correlatedas detailed herein, from about 1.5 to about 4 percent silicon, up toabout 4.5 percent manganese, from about 16 to about 30 percent chromium,up to about 50 percent iron, from about 0.1 to about 1 percent boron,and the balance essentially nickel, in an amount preferably at leastabout 35 percent, the nickel being further correlated such that formolybdenumfree alloys or those containing less than about 2 percentmolybdenum, the nickel content should be maintained below about 49percent and preferably less than about 45 percent. As will be understoodby those skilled in the art, the use of the expression balanceessentially in referring to the nickel content of the alloys does notexclude the presence of other elements commonly present as incidentalconstituents and impurities.

Carbon has been found to contribute to the elevated temperature strengthof the alloy and molybdenum to contribute to the stress-rupture strengthand ductility of the alloy; however, both elements have a detrimentaleffect on weldability. In order to weld the alloy, carbon and molybdenummust be correlated according to the following relationship:

wherein %Mo and %C are in terms of weight percent. Alloys with acalculated carbon and molybdenum level above about 8.5 exhibitheat-affected-zone cracking and cannot be welded. Alloys which exhibitheataffected-zone cracking may be weldable under certain conditions,e.g., thin, unrestrained sections, special welding techniques, etc., butare not considered to be within the purview of this invention. Alloys inaccordance with the foregoing relationship, however, are weldable and,as will be appreciated by those skilled in the art, alloys exhibitingonly weld cracking may be welded using special filler wires. It ispreferred, however, that matching filler wires be employed. It has beenfound that molybdenum and carbon correlated according to the followingrelationship:

will result in alloys having these preferred welding characteristics. Instriving for an optimum combination of properties, e.g., stress-rupturestrength, weldability, etc., it is preferred that molybdenum inaccordance with the foregoing relationships be present in the alloy inamounts of at least about 3 percent, and advantageously, about 6percent.

Silicon and boron are essential for their beneficial effect oncastability. Silicon and boron reduce the melting point of the alloyimproving fluidity and also alter the chemical composition of the oxidefilm on the surface of the molten metal minimizing the formation ofcasting defects such as folds. Silicon and boron also contribute to theoxidation resistance of the alloy.

3 However, the exact mechanism which will explain the theoreticalconsiderations as to why the alloy is weldable, given the high levels ofsilicon and boron, is not presently at hand.

While alloys containing silicon above about 1 percent may be welded, thecastability of the alloy requires that the level of silicon be at leastabout 1.5 percent and preferably 2 to 2.5 percent. Alloys with siliconlevels above about 4 percent are extremely brittle and an upper limit ofabout 3.5 percent is preferred.

The level of boron in the alloy is dependent on the carbon andmolybdenum content. For alloys without molybdenum, boron levels belowabout 0.1 percent and above about 0.5 percent are deemed to have adetrimental effect on weldability. An upper level of about 0.4 percentis preferred. Alloys containing molybdenum and which have carbon levelsbelow about 0.05 percent, are weldable at boron levels from about 0.] toabout 1 percent and greater. It is expected though that at the higherboron levels, the ductility of the alloy would be unsatisfactory and anupper level of about 0.5 percent boron is considered more useful. Forcastability however, it is preferred that the alloys contain boron in anamount of at least 0.2 percent and, advantageously, about 0.3 percent.

Nickel contributes tothe elevated temperature oxidation resistance ofthe alloy and suppresses the embrittling sigma-forming tendencies ofsilicon, manganese and chromium. While the nickel content might beextended down to say, 20 percent, given the chemistry of the otherconstituents, such alloys tend to be brittle in the as-cast conditionand also exhibit severe cracking in the weld heat-affected-zone. In anycase it is most preferred that the nickel level not fall below 30percent and it is of marked benefit that the nickel be about 35 percentor more. The upper limit for nickel is dependent on its effect onweldability and for molybdenumfree alloys or those containing less thanabout 2 percent molybdenum, the nickel content should be maintainedbelow about 49 percent and preferably less than about 45 percent. Alloyscontaining molybdenum above this level, however, may contain nickel inamounts up to about 65 percent, but preferably, about 55 percent.

Chromium is essential in the alloy for oxidation resistance and shouldbe maintained at levels of at least about 16 percent and preferably fromabout 19 to about 24 percent. Also, at the lower limit for chromium,weldability was found to be detrimentally affected in that the weldmentwas susceptible to weld and heat-'affected-zone cracking. Chromium maybe present in amounts up to about 30 percent. At levels above about 30percent, it is suspected that a deleterious intermetallic compound,sigma phase, would form, thereby embrittling the alloy.

Iron in amounts up to about 50 percent, but most advantageously at leastpercent, e.g., percent, can be incorporated in the alloy withoutmaterially affecting the properties. Alloys containing less than about10 percent iron in the thicker sections, e.g., one-half inch or more,tend to be susceptible to heat-affected-zone cracking during the weldingoperation. This range of iron contents also enables use of lessexpensive raw materials, e.g., ferrochrome insteaad of electrolyticchromium, thereby resulting in a significant cost savings.

Manganese contributes to castability and also counteracts thedetrimental effect of sulfur. Manganese above about 4.5 percent has adetrimental effect on weldability however, and a level from about 0.2 toabout 0.8 percent for alloys containing molybdenum and from about 0.5 toabout 3 percent for alloys without molybdenum is preferred.

Solid solution strengtheners such as 'columbiummay also be incorporatedin the alloy to improve elevated temperature properties; columbium atlevels up to about 2.2 percent has been found to produce beneficialeffects in this regard. Columbium, however, appears to have adetrimental effect on the ductility and any benefit to strength must beoffset by the decrease in the duetility of the alloy. Aluminum or othersuitable deoxidation elements may be added to the alloy; it is expectedthough that the castability of the alloy would deteriorate if thealuminum content exceeded about 0.5 percent. Consistent with goodsteelmaking practice, other additives, such as desulfurizing agents andthe like, may also be added to the melt. The phosphorus and sulfurlevels may have an influence on hot-tearing resistance and weldabilityand should be maintained at levels less than about 0.04 percent.However, copper adversely affects weldability. It is an unnecessaryconstituent but if present should be less than about 2 percent andpreferably should not exceed 1 percent.

In accordance with the invention, preferred alloys contemplated hereincontain (by weight) from about 0.005 to about 0.04 or 0.05 percentcarbon, from about 5 to about 8 percent molybdenum, from about 2 toabout 4 percent silicon, from about 0.2 to about 0.8 percent manganese,from about 19 to about 24 percent chromium, up to about 30 percent andparticularly from 10 or 15 to 30 percent, iron, from about 0.1 to about0.5 percent boron, and the balance essentially nickel.

Other preferred alloys in accordance with the invention contemplatedherein contain (by weight) from about 0.8 to about 1.2 percent carbon,from about 2.5 to about 3.5 percent silicon, from about 0.5 to about 3.0percent manganese, from about 19 to about 23 percent chromium, fromabout 30 to about 47 percent iron, from about 0.2 to about 0.4 percentboron, and the balance essentially nickel.

For the purpose of giving those skilled in the art a betterunderstanding of the invention, the following examples are given:

EXAMPLE I Table I sets forth the compositions of Alloys 1 through 16which are examples of alloys within the invention and Alloys A through Ewhich are outside the invention. The series of alloys was air-inductionmelted using a magnesia crucible. Electrolytic nickel, electrolyticmanganese and Armco iron were charged into the furnace and heated to2,850F. Molybdenum pellets were then added followed by silicon-manganese(18 percent silicon, 62 percent manganese, balance iron), electrolyticchromium (Alloy No. l was prepared using ferro-chromium containing aboutpercent chromium), boron in the form of ferro-boron or nickelboron (23percent and 18 percent boron, respectively), electrolytic manganese andmetallic silicon. Columbium, in the form of columbium pellets was alsoadded to Alloy No. 5. The melts were then deoxidized with 0.1 percentaluminum and poured at 2,650F. into green sand Chinese Puzzle patternmolds and green sand single keel block rectangular plate molds havingthe dimensions: (1) inch X l% inches X 12 /2 inches,

(2) A: inch X 2 inches X 12 inches and (3) 1 inch X 3 inches X 12inches. The castings were then shaken from the molds, sandblasted andexamined visually for defects, such as folds.

It should be noted that the Chinese Puzzle pattern molds are designed totest castability characteristics such as the ability of a molten metalto run through the passages of a complex mold with abrupt changes inflow direction that are conducive to turbulence, and comprise a numberof partially adjoining rectangular cavities of about three-sixteenthsinch thickness. The Chinese Puzzle pattern demands more of a melt thansimply the capability to remain fluid over the course of a long run,such as in a fluidity spiral, but requires many TABLE I as evidenced bythe Chinese Puzzle castings which were filled completely withoutevidence of folds or cold-shuts. In contrast, Alloy B, whichis similarin composition to a well known commercial alloy, had unsatisfactorycastability under the same conditions in that numerous folds and poordefinition at the corners resulted.

Test specimens of Alloys 1, 2, 5 and B were machined from the castings(Mold Nos. 1 and 2) and tested at room and elevated temperatures formechanical properties using a standard testing procedures. As can beseen from the results shown here'inbelow in Table 11, the alloys of theinvention exhibit satisfactory tensile properties in both the as-castand heat treated Compositions of Cast Alloys, Weight Percent Alloy C SiMn Ni Cr Mo Fe B Al Other No. 7: 7r 7: 72 7r 7: 7r 7r 7:

1 0.040 3.5 0.5 Bal. 23.9 6.0 30.15 0.35 087 2 0.014 3.1 0.27 Bal. 23.96.1 19.3 0.30 0.09 3 0.017 3.2 0.27 Bal. 24.1 6.0 19.3 0.32 0.11 4 0.552.8 0.57 Bal. 20.3 3.0 19.0 0.31 5 0.02 2.05 N.A. Bal. 20.8 7.9 0.0890.27 0.080 2.2 Cb 6 0.017 2.6 0.53 Bal. 21.9 3.0 19.0 0.31 7 0.010 2.80.57 Bal. 21.9 1.0 19.0 0.31 8 0.015 2.9 1.85 Bal. 20.9 6.2 19.9 0.30 90.011 2.9 4.3 Bal. 20.7 6.3 19.6 0.30 10 0.028 2.9 0.6 Bal. 21.2 6.219.9 0.90 11 0.024 2.8 0.23 Bal. 20.5 6.3 18.5 0.18 Cu 12 0.022 3.2 0.25Bal. 21.9 6.3 18.5 0.38 0.12 13 0.017 3.2 0.22 Bal. 21.0 6.0 15.0 0.250.085 14 0.010 3.2 0.26 Bal. 22.6 6.0 18.9 0.31 0.11 15 0.015 3.1 0.22Bal. 20.5 6.0 5.2 0.28 0.060 16 0.019 3.2 0.22 Bal. 20.5 6.0 9.2 0.35 0070 A 0.55 3.0 0.48 Bal. 20.0 7.0 19.0 0.31 B 0.005 1.2 0.29 Bal. 22.99.2 18.9 N.A. 0.09 C 0.013 2.8 0.23 Bal. 20.5 6.3 18.4 0.20 0.10 1.9 CuD 0.011 3.3 0.23 Bal. 20.5 6.1 19.0 0.38 0.073 3.9 Cu E 0015 3.3 0.23Bal. 20.5 6.1 19.4 0.40 0.077 5.9 Cu

N.A. No! Added.

sharp changes in flow direction with the flow meeting and merging withitself, filling of many corners and flow through and filling of largethin flat surfaces, e.g., l /2 inches square by 3/16 inch thick.

The alloys of the invention had excellent castability TABLE II TensileProperties of Cast Alloys Alloy Mold Test Yield Tensile No. ConditionNo. Temp., Strength Strength Elong, R.A.,

F. psi psi 7: 71

1 As Cast 2 37,400 77,100 18.0 26.0

1 hr. at 2200F.,AC 2 As Cast 2 70 39,800 85,800 15.0 17.0 39.800 78,80011.0 14.0 2 As Cast 2 70 38,300 83,500 16.6 22.0 40,200 83,900 16.5 13.05 As Cast 2 70 46,900 72,700 4.0 7.0 46,300 75,000 5.0 5.5 5 As Cast 270 44,100 85,000 10.0 13.0

1 hr. at 44.900 92,600 15.0 17.5 I 2200F.,AC 5 As Cast 2 1200 32,10070,900 13.0 12.0 5 As Cast 2 1400 31,600 67,600 19.0 15.0 5 As Cast 21600 29,900 64,600 30.0 37.5 B As Cast 2 70 35,300 72,500 38.0 39.036,000 74,700 40.0 34.5 B As Cast 2 70 36,300 68,900 32.5 35.0 38.30080.600 45.5 51.0

AC Air Cooled R.A. Reduction of Area The oxidation resistance of thealloys were compared with commercial alloys by cyclically testingspecimens in an airpercent water atmosphere at l, 000F., using a 24 hourcycle period. The airwater mixture was flowing at 250 cc/min. over thespecimens. which were machined from the castings to a size of 0.3 inchdiameter X 0.75 inch long. At the end of each test period, the specimenswere removed to cool in air. The specimens were then lightly desealed toremove the oxide formed and the weight change of the specimens wasmeasured. Desealing of all the test specimens was done with an S. S.Whiteprecision abrasive cleaning unit using 50 micron alumi na propelledby dry CO A total of 500 hours exposure was employed. The 500 hourexposure weight change results shown hereinbelow in Table 111 evidencethe excellent oxidation resistance of the alloys of the invention ascompared with commercial composition Alloy B and commercially'obtainedalloys Type 310 stainless Steel and HK-40.

TABLE 111 Results of Oxidation Tests To test the weldability of thealloys of the invention, comparative tests were performed by using aBead-on- Plate test, by welding /2 inch butt joints and by welding 1inch butt joints. As is known, the Bead-on-Plate test is primarily ascreening test, the butt-weld being an actual welded joint which showsthe ability of the metal to be welded.

affected-zone cracking and Alloys D and E exhibited severe weld andheat-affected-zone cracking. Alloy A violates the above-describedcarbon-molybdenum relationship. Alloy 8 had very slightheat-affected-zone cracking in one test specimen but the other specimenshowed none, indicating, as will be appreciated by those skilled in theart, a satisfactory base plate material. Alloys 6 and 7, which are belowthe required value of the carbon-molybdenum weldability relationship,exhibited severe weld cracking, indicating the need for a special fillermetal, e.g., a filler made from Alloy 3. The same applies to Alloy 9, analloy relatively high in manganese, i.e., 4.3 percent, and whichexhibited severe weld cracking.

Alloys D and E which are outside of the invention and contained 3.9 and5.9 percent copper, respectively, exhibited severe weld andheat-affected-zone cracking. This is in contrast to the freedom fromweld and heat-affected-zone cracking in the bead-on-plate test exhibitedby Alloy No. l l which contained 0.9 percent copper and by Alloy C whichcontained 1.9 percent copper.

With regard to butt-weld tests, restrained /2-in :h thick butt-weldswere prepared in the various baseplate compositions as described inTable V by manual gas-tungsten arc welding. The base plate was preparedwith a 60 V-bevel edge preparation, 3/32-inch root face and l/l6-inchroot space. Direct-current-straightpolarity was used with an amperagebetween about l 80 and 220 and a voltage of about 16 volts. Argonshielding at a rate of about 25 cubic feet per hour and manual weldingat a rate of approximately 2 to 2.5'inch/min. were employed.Approximately 8 to 10 passes were needed to fill these joints. Afterwelding, /z-ineh wide transverse slices (containing base plate,heat-affectedzone and weld deposit approximately to about 75 percentweld deposit) were cut from the weldment. Approximately eight slicesfrom each weld were ground, polished, etched with Lepitos reagent andexamined for defects at 10X. The compositions of the tiller metals usedare given hereinbelow in Table IV, and the baseplate and filler metaldata in Table V.

TABLE IV Compositions of Filler Metals Filler Metal C Si Mn Ni Cr Mo FeB Other (Alloy No.) 7! 1 7r 7! 72 7c 71 7: 71

I 0.007 0.32 0.26 Bal. 21.8 6.0 19.4 0.13 11 0.007 0.30 0.29 Bal. 22.66.0 19.1 0.29 111 0.031 0.28 0.22 Bal. 21.0 6.1 19.7 0.23 17 0.023 2.900.31 13211. 21.6 6.2 18.5 0 35 F* 0.05 0.40 0.3 61.0 21.5 9.0 4.0 Cb+Ta3.6 G* 0.10 0.50 0.50 Bal. 22.0 9.0 18.5 W 06 "A Commercial Filler MetalThe Bead-on-Plate tests were performed on the cast TABLE V pieces bygrinding the surface and welding a single bead with an automatic gastungsten arc welding ma- Vamch Butt 101MB chine using argon shielding,250 amperes, l 1 volts, dirweld Alloy Finer Mamect-current-stralght-polarity and a travel speed of 16 N0 N0. (AlloyNo.) inches per minute. No filler metal was used in the as 4 D weldedbead. The weld beads were examined for crack- 6 D ing under a microscopeat 10X. Alloys 1 through 15 3 7 D (within the invention) exhibited noheat-affected-zone 2 cracking, whereas Alloy A exhibited severe heat-TABLE V-Continued /2-inch Butt .loints Weld Alloy Filler Mctal No. No.(Alloy N0.)

6 l l 7 2 G 8 2 F 9 l 1 ll 10 C II The /2-inch joint, No. 9 in Table V,in Alloy No. l 1 containing 0.9 percent copper made with the specialcomposition filler No. II was found to be entirely free from weld andheat-affected cracking. However, a similar weld, No. 10, in the 1.9percent copper Alloy C, showed heat-affected-zone cracking. Theseresults, together with the results of the Bead-on-Plate tests, show thatthe alloys of this invention can tolerate a small copper addition suchas that resulting from the use of copper-containing scrap in thepreparation of the charge and that large additions of copper must beavoided in order to retain the desirable weldability characteristic.

All the other /z-inch welds were satisfactory and exhibited freedom fromheat-affected-zone and weld cracking, except Alloys 2, 4 and 7 which hadvery slight weld cracking, less than about one crack per section. Aswill be appreciated by those skilled in the art, this amount of weldcracking is not considered detrimental and meets the requirements as setforth in Military Specification MIL-E-2l562B(SHlPS). The results alsoindicate the ability of the alloy to be welded with both matching andnon-matching filler wires.

In order to further demonstrate the weldability of the alloys of thisinvention, butt-welds were prepared in 1- inch thick plates preparedfrom No. 3 rectangular plate mold castings having a single U-groovejoint preparation. This preparation consisted of a bevel blended to a3/32inch root face by a At-inch radius. Two plates with such edgepreparation were separated by l/16- inch and clamped to a 3-inch thickcast iron platen for welding tests. Gas tungsten-arc welding was usedmanually at a travel speed of about 2 to about 2.5- inch/min., about l6volts, about 180 to 200 amperes direct-current-straight-polarity andargon shielding at about cubic feet per hour. Also, gas metal-arcwelding was used automatically at a travel speed of about 10 inches perminute, about 33 volts, about 300 amperesdirect-current-reverse-polarity, with 0.062-inch diameter wire and argonshielding at about 40 cubic feet per hour. After welding, transverseslices were prepared and examined as previously described for the/2-inch welds.

The l-inch thick weld No. l l was prepared with the manual gastungsten-arc process using filler wire of the same composition as thealloy of this invention, e.g., matching composition filler wire. Thiswire was prepared by casting A-inch dia. rods which were centerlessground to 5/32-inch dia., a suitable form for gas tungsten-arc welding.The joint required 17 passes for completion. A total of 13 polished andetched transverse faces were examined at 10X and found to be entirelyfree from weld and heataffected'zone cracking.

A similar l-inch thick gas tungsten-arc weld, No. 12 in Table VI, wasprepared with a special composition wrought filler wire, identified asIII, in base plate 13 containing 15.0 percent iron. This joint wascompleted in 21 passes and transverse slices were entirely free fromweld and heat-affected-zone cracking.

A third l-inch thick weld, No. 13 in Table VI, was prepared with thespecial wrought filler composition, I, using the gas metal-arc weldingprocess. This 8-pass weld in Alloy 14 was entirely free from weld andheat affected-zone cracking. It is generally known in the WeldingIndustry that the automatic gas metal-arc process provides conditionssignificantly more severe than those imposed by the manual gastungsten-arc welding process and accordingly, further support isprovided for the exceptional weldability of the alloy of this invention.

Weld Nos. 14 and 15 in Table V] were l-inch thick butt-joints in basealloys 15 and 16 which contained 5.2 percent and 9.2 percent iron,respectively. Both joints were completed in 21 passes using the manualgas tungsten-arc welding process. Microscopic examination of transverseslices, cut from these welds, showed the presence of cracks within theheat-affected zone of both. This behavior is distinctly different fromthe behavior shown previously for weld Nos. 1 l, 12 and 13 of thisinvention. As previously mentioned herein, alloy with less than about 10percent iron tend to exhibit susceptibility to cracking in theheat-affected zone in thick sections. It is most beneficial that thealloys of this invention contain more than 10 percent iron to minimizesusceptibility to heat-affected-zone cracking.

To test the stress-rupture properties of the alloys, the transverseslices from the butt welds described hereinabove were machined into testbars containing weld metal, heat-affected zone and base metal(approximately 50 percent to about percent weld deposit). Thestress-rupture properties were then measured at l,600F. using standardtesting procedures. The results shown hereinbelow in Table VII reflectthe excellent stress-rupture properties of the alloys of the inventionand show that sound welds are produced without degrading the base metalproperties.

A comparison of welds 2 and 3 in Alloys 6 and 7 demonstrate thebeneficial effect of molybdenum on the stress-rupture life of the alloy.Alloys 6 and 7 are comparable in composition except for the molybdenumcontents which are 3 percent and 1 percent, respectively.

TABLE V11 TABLE VIII-Continued Stress-Rupture Properties of Welds WeldBase Filler No. Alloy Metal No. Alloy Stress Life Elong.. R.A.. FractureNo. psi hrs. 72 (1") '71 Location 4 3 3 10.000 23.1 30.0 52.5 Base 8.000139.9 20.0 51.7 Base 6,000 496.6 7.0 2.5 Weld 5 3 11 8.000 56.5 26.054.3 Base 6.000 692.5 24.0 53.0 Base 10.000 21.0 26.0 61.5 Base 8 2 F8.000 106.0 23.0 61.0 Base 6,000 378.3 29.0 52.8 Base 10.000 10.7 19.047.3 Base 1 4 D 8,000 66.2 18.0 25.5 Base 6,000 317.6 8.0 17.0 Base10.000 52.1 12.0 29.0 Base 2 6 8.000 154.3 8.0 24.4 Base 6.000 456+ 3 7D 8.000 17.6 21.0 37.8 Base 6.000 48.5 18.0 40.3 Base 10.000 13.6 21.058.6 Base 13 14 1 8.000 75.7 11.0 35.3 Base 6.000 835.7 11.0 19.0 BaseEXAMPLE 11 Table V111 sets forth the compositions of Alloys 18 through29, alloys within the invention, and Alloys H through R, alloys outsidethe invention, having been prepared and cast following the proceduresdescribed in Example I except that molybdenum was not added to themelts. Alloy 25 was not cast into molds 1, 2 and 3 but was cast into asimilar mold (double keel) having the dimensions 1 inch X 1% inches X 7%inches (Mold No. 4). The alloys of the invention had excellentcastability as evidenced by the Chinese Puzzle castings which werefilled completely without evidence of folds or cold shuts. In contrast,a commercial composition HU Alloy having the nominal composition (inweight percent) 0.45 percent carbon, 1.6 percent manganese, 1.6 percentsilicon, 20.7 percent chromium, 38.8 percent nickel, balance ironexhibited folds when poured at the same temperature and, when thepouring temperature was increased to eliminate the folds, other defectssuch as hot tears and solidification shrinkage appeared.

TABLE VIII Compositions of Cast Alloys. Weight Percent Alloy C Si Mn NiCr B Al Fe No. 7: 7: 7c 7( 7r 7: 7c 71 18 0.95 3.17 2.09 39.7 19.5 0.270.055 Bal. 19 0.97 2.8 2.15 39.7 21.5 0.34 0.040 Bal. 20 0.98 3.02 0.7438.5 20.1 0.32 0.086 Bal. 21 0.9 2.76 2.28 40.5 20.0 0.13 0.01 8:11. 220.91 2.90 1.86 38.8 20.1 0.14 0.063 Ba]. 23 0.90 3.07 1.48 39.9 19.4 0.30.08 Ba]. 24 0.80 1.99 2.32 39.9 20.4 0.14 0.04 Ba]. 25 0.98 2.77 2.3439.7 21.3 0.24 0.13 8:11. 26 1.03 2.90 1.90 41.9 18.6 0.29 0.11 Bal. 271.08 3.20 1.80 29.5 21.1 0.24 0.005 Bal. 28 1.01 3.10 1.39 38.5 19.60.28 0.12 Bal. 29 1.00 3.12 1.00 38.4 20.0 0.32 0.11 Bal. H 1.50 3.101.90 39.7 20.7 0.26 0.005 Bal. 1 1.08 3.00 4.60 39.7 20.6 0.27 0.005B211. .1 0.97 2.97 2.36 40.4 20.5 0.53 0.10 Bal. K 1.05 2.90 2.00 49.019.8 0.26 0.005 Bal. L 1.10 2.90 1.90 38.8 15.7 0.24 0.005 Bal. M 1.090.93 1.80 39.8 20.6 0.27 0.039 Bal. N 1.12 3.20 1.80 19.9 21.1 0.260.005 B211. 0 0.87 2.90 1.80 39.1 19.7 N.A. 0.068 Bal.

Compositions 01 Cast Alloys. Weight Percent N.A.= Not Added I Testspecimens of Alloys 18 and 20 were machined from the castings (Mold Nos.1 and 2 described hereinabove in Example I) and tested at room andelevated temperatures for mechanical properties using standard testingprocedures. Alloy 25 was welded with a matching composition filler wireas a /2-inch butt-weld by manual gas tungsten-arc welding as describedhereinabove in Example I. Tensile specimens were machined from thetransverse slices of the weldment and contained base plate,heat-affected-zone and weld deposit (about 50 to about percent welddeposit). For comparison purposes also shown hereinbelow in Table 1X aretensile values of commercial alloy (l-lU) obtained from the AmericanCasting Institute Data Sheet for Heat Resistant Type HU, issued March1957.

Failure outside of weld in base plate Commercial alloy HU Oxidationtests were also conducted in respect of versions of the molybdenum-freealloys of Table V111 as well as a few comparative alloys. The procedureswere identical to those described hereinbelow. Specimens were eithermachined from the castings (as-cast) or from /z-inch butt-welds(as-welded). The as-welded specimens included the base-plate,heat-affected zone and weld deposit (approximately 50 to about 75percent weld deposit). The results are given in Table X.

As can be seen from the data, the alloys of the invention exhibitexcellent oxidation-resistance in both the as-cast and as-weldedconditions as compared to commercial alloys. The relatively lowoxidation-resistance of Alloy 24 can be attributed to the siliconcontent which is below the preferred range of the alloy, i.e., 2.5percent. Alloy 0 demonstrates the effect of not including boron in thealloy as this alloy has a relatively low oxidation resistance.

TABLE x Results of Oxidation Tests Alloy No. Condition Dcscaled WeightChange mg/cm 18 As-Cast 5.95

19 As-Welded 7.04 24 As-Cast 18. 10 -25.72

26 AsWelded 8.42

27 As-Welded 6.50 2 8 As-Welded 5 .79 29 As-Welded 4.77 O As-Cast 18.381 8.28

P As-Cast 9.76 (l) Wrought and 5.21

Annealed (2) Wrought and 1 1.7

Annealed l commercially obtained Hustelloy X (2) commercially obtainedType 310 S.S.

To determine weldability behavior, the alloys in Table VIII were testedusing the Bead-on-Plate test and several by welding a A a-inchbutt-welded joint, as described hereinabove in Example I.

As to the Bead-on-Plate tests, none of the preferred alloys exhibitedheat-affected-zone cracking. Alloys H through M, which are outside theinvention, showed both severe heat-affected-zone and weld cracking andare thus unsatisfactory as base plate materials. Alloy did not exhibitany heat-affected-zone cracking but exhibited severe weld cracking.Alloys Q and R exhibited weld and heat-affected-zone cracking and thisis attributable to a carbon content below the preferred level and asilicon content above the preferred level, respectively.

The /2-inch buttweld joints were made from Alloys 19, 22, and 23 andAlloy N with matching filler wires. None of the joints exhibited weldcracking; however, Alloy N, which is outside the invention, exhibitedsevere heat-affected-zone cracking. This may be attributed to the lownickel content of 19.9 percent.

To test the stress-rupture properties of the alloys of the invention,specimens of Alloys 19 and 23 were machined and tested (in the as-castcondition) at 1,600F. The results as shown hereinbelow in Table XIindicate the excellent stress-rupture properties of the cast alloy. Thestress-rupture life of Alloy 19 at the 8,000 psi stress level is lowprobably due to a casting defect and should not be regarded asrepresentative of the alloys stress-rupture property.

Transverse slices of a /2-inch butt-weld of Alloy 22 (prepared asdescribed hereinabove) was also tested and, as can be seen from theresults, exhibits excellent stress-rupture properties. The weld wasprepared using the procedures described hereinabove and the filler wire,identified as I in Table IV, contained 21.8 percent chromium, 19.4percent iron, 6.0 percent molybdenum, 0.13 percent boron and the balanceessentially nickel.

TABLE XI Stress-Rupture Properties The alloys of the invention areespecially useful in high temperature oxidizing atmosphere applications.They may be employed in many other applications, including hightemperature applications where resistance to corrosion and good creepand rupture properties are required. The alloys are particularly usefulas static components in vehicular turbines.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

We claim: v

1. A highly castable and weldable heat resistant alloy affording hightemperature oxidation resistance consisting essentially of (by weight)up to about 1.4 percent carbon, less than 8.5 percent molybdenum, thecarbon and molybdenum being specially correlated according to thefollowing relationship:

from about 1.5 to about 4 percent silicon, up to about 4.5 percentmanganese, from about 16 to about 30 percent chromium, up to about 50percent iron, from about 0.1 to about 1 percent boron for alloyscontaining molybdenum and from about 0.1 to about 0.5 percent for alloyswithout molybdenum, and the balance, in an amount of at least about 35percent, essentially nickel, the nickel being further correlated suchthat for alloys not containing molybdenum, the nickel content does notexceed about 49 percent.

2. An alloy in accordance with claim 1 wherein the carbon and molybdenumare correlated according to the following relationship:

3. An alloy in accordance with claim 1 containing from about 0.005 toabout 0.05 percent carbon, from about 5 to about 8 percent molybdenum,from about 2 to about 4 percent silicon, from about 0.2 to about 0.8percent manganese, from about 19 to about 24 percent chromium, up toabout 30 percent iron and from about 0.1 to about 0.5 percent boron.

4. An alloy in accordance with claim 3 wherein the carbon and molybdenumare correlated according to the following relationship:

5. An alloy in accordance with claim 1 containing at least about 10percent iron.

6. An alloy in accordance with claim 1 containing at least about 15percent iron.

7. An alloy in accordance with claim 1 containing from about 0.005 toabout 0.05 percent carbon. from about to about 8 percent molybdenum,from about 2 to about 4 percent silicon, from about 0.2 to about 0.8percent manganese, from about 19 to about 24 percent chromium, fromabout to about 30 percent iron and from about 0.1 to about 0.5 percentboron.

8. An alloy in accordance with claim 1 containing from about 0.005 toabout 0.05 percent carbon, from about 5 to about 8 percent molybdenum,from about 2 to about 4 percent silicon, from about 0.2 to about 0.8percent manganese, from about l9 to about 24 percent chromium, fromabout to about 25 percent iron and from about 0.1 to about 0.5 percentboron.

9. An alloy in accordance with claim 1 containing from about 0.8 toabout 1.2 percent carbon, from about 2.5 to about 3.5 percent silicon,from about 0.5 to about 3.0 percent manganese, from about 19 to about 23percent chromium, from about 30 to about 47 percent iron, and from about0.2 to about 0.4 percent boron.

10. An alloy in accordance with claim 9 containing less than about 45percent iron.

11. As a new article of manufacture. a welded assembly of the alloy asset forth in claim 1, exhibiting freedom from cracking in sections of/2-inch and greater thicknesses.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 13,892,541

DATED July 1, 1975 INVENTOR(S) Robin Mackay Forbes Jones and WalterAdrian Petersen it is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 3, line 8, for "to" read or line 63, for "insteaad" read insteadCol. 5, last column of Table II (R.A. bottom line,

omit l5 O" Col. 12, last column of Table IX, for "R.A. Q 10" read Signedand Sealed this sixteenth Day Of September 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oflarenrsand Trademarks

1. A HIGHLY CASTABLE AND WELDABLE HEAT RESISTANT ALLOY AFFORDING HIGHTEMPERATURE OXIDATION RESISTANCE CONSISTING ESSENTIALLY OF (BY WEIGHT)UP TO ABOUT 1.4 PERCENT CARBON, LESS THAN 8.5 PERCENT MOLYBDENUM, THECARBON AND MOLYBDENUM BEING SPECIALLY CORRELATED ACCORDING TO THEFOLLOWING RELATIONSHIP:
 2. An alloy in accordance with claim 1 whereinthe carbon and molybdenum are correlated according to the followingrelationship: 5.4 <%Mo + 6(%C) <8.5
 3. An alloy in accordance with claim1 containing from about 0.005 to about 0.05 percent carbon, from about 5to about 8 percent molybdenum, from about 2 to about 4 percent silicon,from about 0.2 to about 0.8 percent manganese, from about 19 to about 24percent chromium, up to about 30 percent iron and from about 0.1 toabout 0.5 percent boron.
 4. An alloy in accordance with claim 3 whereinthe carbon and molybdenum are correlated according to the followingrelationship: 5.4 <%Mo + 6(%C) <8.5.
 5. An alloy in accordance withclaim 1 containing at least about 10 percent iron.
 6. An alloy inaccordance with claim 1 containing at least about 15 percent iron.
 7. Analloy in accordance with claim 1 containing from about 0.005 to about0.05 percent carbon, from about 5 to about 8 percent molybdenum, fromabout 2 to about 4 percent silicon, from about 0.2 to about 0.8 percentmanganese, from about 19 to about 24 percent chromium, from about 10 toabout 30 percent iron and from about 0.1 to about 0.5 percent boron. 8.An alloy in accordance with claim 1 containing from about 0.005 to about0.05 percent carbon, from about 5 to about 8 percent molybdenum, fromabout 2 to about 4 percent silicon, from about 0.2 to about 0.8 percentmanganese, from about 19 to about 24 percent chromium, from about 15 toabout 25 percent iron and from about 0.1 to about 0.5 percent boron. 9.An alloy in accordance with claim 1 containing from about 0.8 to about1.2 percent carbon, from about 2.5 to about 3.5 percent silicon, fromabout 0.5 to about 3.0 percent manganese, from about 19 to about 23percent chromium, from about 30 to about 47 percent iron, and from about0.2 to about 0.4 percent boron.
 10. An alloy in accordance with claim 9containing less than about 45 percent iron.
 11. As a new article ofmanufacture, a welded assembly of the alloy as set forth in claim 1,exhibiting freedom from cracking in sections of 1/2 -inch and greaterthicknesses.